292 



The Bird 



New York Zoological Park, I have had opportunity to 

 record many cases of the effect of food upon colour. An 

 experiment very commonly known is that of feeding 

 canaries on red pepper, thus causing their plumage, after 



Fig. 232. — Variation due to climate, etc., in races of North American Song Sparrows. 

 (From a photograph provided by the American Museum of Natural History.) 



successive moults, to become of an intense orange colour. 

 This is the more remarkable since the actual red pigment, 

 or capsicin, of red pepper is not the direct cause of the 

 canaries' changed hue, but a fatty substance known as 

 triolein, which is a constituent of the pepper. 



